Objective: The McGrath Video laryngoscope is a newly developed video
laryngoscope that significantly improves laryngeal view and facilitates
endotracheal intubation in difficult airways. However in patients with
normal airway that is not mentioned before. The aim of this study was to
compare the McGrath video laryngoscope with the Macintosh laryngoscope
in patients with normal airways.

Methods: A total of 100 patients requiring orotracheal intubation,
were randomized to either having intubation with the McGrath video
laryngoscope or the Macintosh laryngoscope. The primary outcome was the
laryngoscopy view using percentage of glottic opening (POGO) score.
Secondary outcomes included Cormack and Lehane grading system, time to
intubation, number of failed intubations, number of attempts before
successful intubation and hemodynamic parameters during intubation.

Results: POGO scores were significantly higher in the McGrath group
compared with the Macintosh group (p<0.001) despite time to
successful intubation was similar in both groups. The McGrath video
laryngoscope provided more Grade-I laryngoscopic views than the
Macintosh laryngoscope (p0.05).

Tracheal intubation is an important step in securing airway patency
during general anesthesia. Hence, rapid, flawless, successful intubation
process is of primary importance for anesthesiologists. Macintosh direct
laryngoscope is the most commonly used laryngoscope in the intubation of
the patients. In the presence of difficulty at intubation, complications
such as dental injury, laryngospasm, bronchospasm, and severe
complications such as hypoxia, hypercarbia, and death can occur as a
result of multiple intubation attempts.1

Therefore, many alternative devices have been developed to
facilitate smooth intubation, and the utility and benefits of these
devices have been compared in various studies. Video laryngoscopes are
at the top of the list of devices developed for the purpose of smooth
intubation. This device has many types and the number of such devices is
increasing every passing day.

We studied one such alternative intubation device: the McGrath(r)
Series 5 video laryngoscope (Aircraft Medical Ltd, Edinburgh, UK). The
McGrath video laryngoscope is designed to provide a better laryngeal
view than that obtained by direct laryngoscopy with a Macintosh
laryngoscope. It also provides that with a high-resolution video camera
placed within an angulated single-use blade of adjustable length.
Several studies have reported improved laryngoscopic views and greater
intubation success rates in patients with predicted and known difficult
airways using the McGrath video laryngoscope.2-7 However, there are no
prospective and randomized clinical trials comparing the McGrath video
laryngoscope with the Macintosh laryngoscope in patients with normal
airways. The primary outcome was the laryngoscopic view using percentage
of glottic opening (POGO) score with both devices.

Secondary outcomes included Cormack and Lehane grading system, time
to intubation, number of failed intubations, number of attempts before
successful intubation, complications and hemodynamic parameters during
intubation.

METHODS

After obtaining approval from local Institutional Review Board
(Necmettin Erbakan University Meram School of Medicine Ethics Committee)
and registration from the Australian New Zealand Clinical Trials
Registry (registration number: ACTRN12614000910606), we recruited 100
patients of ASA physical status 1-2 who were scheduled for elective
surgery under general anesthesia requiring tracheal intubation.

Airway difficulty score (ADS)1 was assessed prior to intubation in
order to exclude those predicted to make the procedure difficult.
Patients with an ADS score above 8 and thyroid-to-chin length of 5 cm or
shorter, a Mallampati class 3 or higher, mouth opening <3cm,
restriction in neck extension or protruding front teeth were predicted
to be difficult in intubation and/or airway and were thus excluded from
the study. Also, patients were excluded from the study if they required
rapid sequence induction, had a history of previous difficult direct
laryngoscopy and had uncontrolled hypertension, ischemic heart disease,
acute or recent stroke or myocardial infarction, cervical spine
instability or cervical myelopathy, symptomatic asthma or reactive
airway disease and history of gastric reflux.

After obtaining written informed consent, patients were assigned, by
using a computer-generated block randomisation, to laryngoscopy with
either McGrath video laryngoscope or the Macintosh laryngoscope. All
tracheal intubations with both the Macintosh laryngoscope and McGrath
video laryngoscope were performed by one anesthesiologist who had used
both devices more than 50 times clinically.

All patients were expected to fast 6-8 hours before surgery, and no
one premedicated. With the patient placed in the supine position,
routine monitors (consisting of a pulse oximeter, 3-lead ECG and a
non-invasive blood pressure cuff) were applied. Baseline measurements
were obtained and three minutes of pre-oxygenation was performed before
the induction of general anesthesia. Standardize anesthetic induction
was performed with 1 mcg/ kg fentanyl, 1-2 mg/kg of propofol, and when
consciousness was lost, 0.6 mg/kg of rocuronium was injected. After,
making sure that all four TOF responses of the adductor pollicis
disappeared, which ensures sufficient muscular blockade, intubation was
then performed. Number 3 or 4 blades was used in all patients. A size
7.0 mm tracheal tube was used to intubate the trachea in female
patients, and a size 7.5 mm tube was used for all male patients.

If more than one intubation attempt was required, the patient
received bag-and mask ventilation between attempts and various maneuvers
were employed, including external laryngeal pressure, readjustment of
the stylet and use of a bougie. Failed intubation was defined as failure
after three attempts and a pre-determined alternative airway management
plan was instituted by the treating anesthetist. Correct placement of
the tracheal tube was confirmed by capnography and bilateral chest
auscultation.

The primary outcome was the laryngoscopic view using percentage of
glottic opening (POGO) score (0 to 100%, 100 = full view of glottis from
anterior commissure to the inter-arytenoid notch, 0 = even
inter-arytenoid notch is not seen). Secondary outcomes included Cormack
and Lehane grading system (including 1-4), time to intubation, number of
failed intubations, number of attempts before successful intubation and
hemodynamic parameters (HR: Heart rate, MBP: Mean blood pressure) during
intubation. Minor complications like oropharyngeal trauma or mucosal
bleeding were also recorded. These data were collected by one
independent observer. The time taken for successful tracheal intubation
was measured from the time the allocated laryngoscope was inserted in
the patient's mouth until end-tidal carbondioxide was detected.

To ensure that the sample sizes of the study groups would support a
valid comparison, a power analysis was performed (a = 0.05, b = 0.90),
which indicated that at least 46 subjects should be recruited for each
group. For this calculation, we used the mean (67.6) and SD (24.7) of
the POGO score with Macintosh laryngoscope, in that study 8 and assumed
a 25% increase of POGO score from the Macintosh laryngoscope POGO score
value with McGrath laryngoscope. Therefore, we recruited 100 patients in
total to account for possible drop-outs.

The Mann-Whitney U-test was used to analyze the time for successful
intubation and independent t-test used for POGO scores. The Fisher exact
test was used to analyze the Cormack and Lehane view at laryngoscopy,
the number of intubation attempts and the number of failed intubations.
For variables with multiple measurements (hemodynamic variables), a
repeated measures analysis of variance was used to evaluated the effects
of time and group assignment, while two-way analysis of variance was
used to compare the difference within the groups.

Table-I: Comparison of patients' baseline characteristics
between the Mc Grath and Macintosh groups. Values are mean (SD) or
number.

###Macintosh###Mc Grath###p value

###Group (n=50)###Group (n=50)

Age (Year)###40.36 (14.67)###39.46 (15.58)###0.771

Gender###17/33###23/27###0.112

(Male/Female)

BMI (kg/m2)###24.97 (4.13)###24.23 (3.41)###0.346

RESULTS

The baseline characteristics of the patients were similar in both
groups, as shown in TableI. The median time taken to perform successful
intubation was similar in the McGrath group when compared with the
Macintosh group (mean 18.93 vs 19.68 s, median 18 vs 18 s, IQR 15-21.5
vs 15-23; Fig.1).

The results of the Cormack and Lehane grade, percentage of glottic
opening during laryngoscopy, number of intubation attempts, failed
intubations and complications are summarized in Table-II. The McGrath
video laryngoscope provided a significantly better laryngoscopic view
compared with the Macintosh laryngoscope. POGO scores were significantly
higher in the McGrath group compared with the Macintosh group
(p<0.001). The McGrath video laryngoscope provided more Grade-I
laryngoscopic views than the Macintosh laryngoscope (p<0.001).
Although number of more than one attempts in order to achieve successful
intubation was significantly higher in the Macintosh group compared with
the McGrath group (p=0.001), there were no failed intubation in both
groups. There were in total fifteen minor oropharyngeal mucosal injuries
as a result of the intubation, two from using the McGrath video
laryngoscope and thirteen from the Macintosh laryngoscope. This
difference was statistically significant (p=0.004).

Table-II: Comparison of the laryngoscopic view, POGO score, the
number of intubation attempts and the number of failed intubations
between the Mc Grath and Macintosh groups.

###Macintosh###McGrath###p value

###group (n=50)###group (n=50)

CL laryngoscopic###1###23###40###<0.001

view###[greater than or equal to]2###27###10

POGO score (%)###60.80 (35.49)###84.67 (19.39)###1###7###0

No. of failed intubations###0###0

Minor complications###13###2###0.004

Mucosal bleeding

The results of hemodynamic parameters. In both groups, there were no
significant changes in heart rate (HR) and mean blood pressure (MBP)
from baseline to post intubation (Immediately after intubation and two
minute after intubation) (p>0.05) are shown in Table-III. There was
no statistically significant difference in the changes between the two
groups (p>0.05).

DISCUSSION

Compared with the Macintosh laryngoscope, the McGrath video
laryngoscope improved the laryngeal view in patients with normal airway.
The McGrath video laryngoscope was also superior in terms of intubation
attempts and minor complications. Despite all these advantages there was
no significant difference in duration of intubation.

Table-III: Comparison of the hemodynamic parameters between the
McGrath and Macintosh groups. Values are number or mean (SD).

###Macintosh###McGrath###p value

###group (n=50)###group (n=50)

HR_t0 (beat/min)###83.90 (12.77)###80.35 (13.83)###0.194

HR_t1###90.94 (12.31)###88.48 (13.47)###0.352

HR_t2###84.88 (12.74)###81.35 (13.30)###0.187

MBP_t0 (mmHg)###93.16 (10.95)###91.87 (11.49)###0.575

MBP_t1###101.28 (15.01)###102.98 (18.20)###0.618

MBP_t2###92.88 (14.38)###90.46 (14.96)###0.421

The studies that used various video laryngoscopes including the
Macintosh laryngoscope and McGrath video laryngoscope on patients with
normal airways and on manikins have reported intubation times similar to
our study.5,8-10 Consistent with our findings, the studies that compared
video laryngoscope with the Macintosh laryngoscope reported higher POGO
score and higher Grade I laryngoscopic view in video laryngoscope
groups.8,10 Some studies that evaluated intubation times on manikins
have reported different results compared to our study. Among these
studies, Kim et al. compared the McGrath video laryngoscope with the
Glide Scope Ranger portable video laryngoscope, and they reported a
two-fold longer intubation times in the McGrath video laryngoscope group
compared to our study.11

Different from our results, another study performed on manikins
reported longer intubation times in the McGrath video laryngoscope group
(median time: 40.7 sec, IQR: 31.0-57.4) compared to the Macintosh
laryngoscope group.12 In another manikin study Ruetzler et al. compared
five video laryngoscopes and conventional direct laryngoscopy on simple
and simulated difficult airways on the intubation trainer.13 Similarl to
our findings they revealed in the normal intubation setting, time to
intubation ranged from 16.0 s (conventional direct laryngoscopy) to 34.3
s (McGrath).

However, it must be kept in mind that intubation times in the
Macintosh laryngoscope group in that study (median time: 26.1 sec, IQR:
19.9-33.5) were longer compared to intubation times in our study in the
Macintosh laryngoscope group. Higher intubation times reported in these
two studies compared to our study are considered to be caused by the
fact that these studies were conducted on manikins.

The studies that used the McGrath video laryngoscope in patients
with difficult airways revealed an intubation time ranging between 35
and 50 seconds.2,14,15 Among these studies, the study comparing the
Macintosh laryngoscope with the McGrath video laryngoscope detected
longer intubation times in the McGrath video laryngoscope group.2
Likewise, although shorter intubation times were achieved with the
Henderson direct laryngoscope compared to the McGrath laryngoscope, the
difference was not statistically significant.15 These periods are
different than those found in the present study due to the differences
in the patient population. Although intubation times were longer in the
McGrath video laryngoscope group, the rate of acquiring a Cormack and
Lehane Grade I laryngoscopic view was significantly higher in the
McGrath video laryngoscope group.

Parallel to this, the percentage of glottic opening (POGO) score was
higher in the McGrath video laryngoscope group compared to the Macintosh
laryngoscope group.2 The present study found similar results in terms of
the POGO score and the rates of the Cormack and Lehane laryngoscopic
view.

In a study in which inexperienced anesthesiologists used the McGrath
video laryngoscope and the Macintosh laryngoscope, the mean intubation
time in the McGrath video laryngoscope group (median time: 47.0 sec,
IQR: 39.0-60.0) was significantly higher compared to the Macintosh
laryngoscope group (median time: 29.5 sec, IQR: 23.0-36.8).16 In spite
of this, the number of patients with whom the Cormack and Lehane Grade I
laryngoscopic view was obtained, was higher in the McGrath video
laryngoscope group. However, the overall rate of successful tracheal
intubation was similar in both groups. Similar intubation times were
found in a study comparing novice users of the McGrath video
laryngoscope with the Macintosh laryngoscope on manikins. However, the
rate of the Cormack and Lehane Grade I laryngoscopic view was
significantly higher in the McGrath video laryngoscope group.17

Furthermore, in this study, novices achieved a higher overall rate
of successful tracheal intubation when using the McGrath video
laryngoscope. In a study about tracheal intubation with a McGrath(r)
Series 5 video laryngoscope by novice personnel in a
cervical-immobilized manikin, similar to our results first-attempt
success rate was higher for the McGrath(r) Series 5 compared to the
Macintosh laryngoscope (84.2% vs. 47.7%, respectively).18 In this study
number of more than one attempts in order to achieve successful
intubation was significantly higher in the Macintosh group compared with
the McGrath group.

The studies in the literature have found different results in terms
of minor complications. Some studies comparing the McGrath video
laryngoscope with the Macintosh laryngoscope, in contrast to our
findings, reported no difference between minor complication rates,2,16
while some studies have findings similar to our study.17 In addition,
one study that compared the McGrath video laryngoscope with C-MAC video
laryngoscope showed no difference in terms of the rates of minor
complications, while the number of intubation attempts was higher in the
McGrath group. 14

Furthermore, there was no significant difference in the proportional
change in hemodynamic parameters, similar to our findings. There was
also no significant difference between McGrath video laryngoscope and
Macintosh laryngoscope groups in terms of hemodynamic parameters.

In conclusion, the McGrath video laryngoscope produces excellent
laryngoscopic views in patients with normal airways, so the practitioner
may more easily and comfortably carry out intubation and consider it as
the instrument of choice.